In the past, paints, lacquers, adhesives, insulating resinous foams and kindred products have been specially formulated for spray application from hand-held, pressurized containers of the "aerosol" type. However, many of these products have been compromised from their optimum properties by the special formulation requirements for this mode of utilization. Other products have resisted successful re-formulation altogether. Furthermore, a primary concern in the formulation of polymerizable, reactable, or curable products for "aerosol" dispensing is the assurance of adequate shelf-life or pot-life in the container; and the desire to achieve commercially acceptable storage-life has heretofore involved such approaches as the provision of two separate containers for the reactable components, in conjunction with individual valving and a common mixing nozzle. Boe et al U.S. Pat. No. 3,096,001 discloses such an arrangement. Another approach relies on a selectively rupturable, partition membrane, such as is taught in Brooks et al U.S. Pat. No. 3,295,724. Both of these systems are prone to produce generally unacceptable variation from the targeted stoichiometric proportion of the various ingredients and concomitant unpredictability in the performance of the resultant product.
In addition, a particularly critical shelf-life problem exists with aerosol-packaged pre-polymerized urethane products because of the propensity that these compositions display for progressive enviscosation and ultimate solidification upon prolonged storage, especially when packaged with cure-accelerators or with reactive blowing agents. Formulation of such products so as to realize, in the cured state, the optimum combination of strength, toughness and rigidity, as a consequence, has resulted in drastically abbreviated shelf-life.